Placement of polarizing plates on both sides of a glass substrate, which forms the outermost face of a liquid-crystal panel, is indispensable for a liquid crystal display because of the picture formation system adopted therein, and a polarizing plate is generally stuck on the outermost face of a liquid-crystal panel. In addition, there is a considerable growth in the use of various optical elements besides the polarizing plate on the outermost face of a liquid-crystal panel with the intention of further enhancing display quality. For instance, a retardation plate for prevention of coloring, a viewing angle enlarging film for widening a viewing angle and a brightness enhancement film for enhancing contrast and so on are used. These films are collectively referred to as optical films.
When the optical films as recited above are bonded, an adhesive is generally used in order to prevent losses due to reflection of light from the interfaces. In addition, the adhesive is previously provided on one side or both sides of an optical film as a adhesive layer because of its advantages that it can fix the optical film instantaneously, eliminate the necessity for the optical film to undergo a drying process for fixation, and so on. In other words, adhesive-type optical films are generally used in bonding optical films to a liquid-crystal panel and the like.
When the aforementioned adhesive-type optical films are, e.g., transported, handled, or conveyed on the manufacturing and processing-operation lines, a defective situation, specifically a phenomenon that the adhesives in edges of the adhesive-type optical films are dropped out in a chipped state due to contact between the optical films' ends and substances of some kinds (hereinafter referred to as “adhesive chips”), is brought about at externally unprotected side faces of the adhesive layers. In addition, there occurs a case where dropped-out adhesive contaminates the surfaces of optical films (hereinafter referred to as “adhesive contamination”). If once adhesive chips occurs, secure bonding becomes impossible, and what is worse, the chipped parts form an air layer and come to have different refractive index and vibration direction from other parts, thereby becoming a cause of defective display. Likewise, the adhesive contamination also causes defective display.
For prevention of such adhesive chips and adhesive contamination, the method of attaching powder to edges of an adhesive layer (see, e.g., Patent Document 1), the method of forming a non-tack layer on edges of an adhesive layer by spray coating (see, e.g., Patent Document 2), or the method of molding the side faces of an adhesive-type optical film into a projection-and-depression repeat structure (see, e.g., Patent Document 3) have so far been adopted. However, these methods involve contamination with an extraneous substance, such as powder or a sprayed coat, or require complex processes. Therefore, simpler and easier methods have been sought.    [Patent Document 1] JP 2001-272539 A    [Patent Document 2] JP 2000-258627 A    [Patent Document 3] JP 2001-033623 A